It is well known that proximal third and/or mid-shaft humeral fractures are often best mended using a retrograde humeral nailing technique in order to avoid disturbing the rotator cuff or the subacromial space. In a typical surgical technique of this type, a longitudinal incision is made through the skin and underlying tissue in order to identify and expose the olecranon fossa in the posterior humerus and the region just proximal to the olecranon fossa. In the prior art technique, a drill is then used to open the posterior humeral cortex about 21/2 centimeters from the proximal--most extent of the olecranon fossa. This initial opening is generally made along an axis substantially perpendicular to the bone axis. Because the nail must enter the bone at a relatively low angle, the opening must be elongated, generally by the use of a small curved awl or a ronguer.
Unfortunately, this technique of enlarging an original pilot hole into an oblong opening to facilitate receiving the humeral nail can sometimes result in unnecessary bone damage due to the increased pressure caused by the hole enlarging device. This increased pressure may even crack the bone at the thin bone location, which can be on the order of about 1/16 of an inch in thickness. This technique is also undesirable in that it almost always inevitably leads to the removal of more bone cortex than is actually necessary to insert the retrograde humeral nail. After the entry hole is made sufficiently oblong and large to accommodate a humeral nail at a low angle, any and several known techniques can be utilized to finally implant the nail within the humerus.
The present invention is directed to overcoming problems associated with prior art methods of making an entry hole to implant an intramedullary nail across a fracture in an elongated bone, especially as it relates to an entry hole for a retrograde humeral nail.